In the U.S., Corporate Average Fuel Economy (CAFE) regulations mandate a specified, gradual increase of a corporate fleet's overall fuel economy by established target dates. In conjunction, industry-wide research and development has also been undertaken to improve fuel economy through new engine design and importantly through new approaches to lubricating oil formulating. Lubricant optimization is especially preferred over engine hardware changes due to its comparative lower cost per unit in fuel efficiency and possibility for backward compatibility with older engines.
Engine oil acts as a lubricant between moving engine parts at various conditions of load, speed and temperature. Hence, the various engine components experience different combinations of boundary layer, mixed and (elasto) hydrodynamic regimes of lubrication; with the largest frictional losses at piston liner/piston ring interface and a smaller part by the bearing and valve train. To reduce the energy losses due to friction of the various parts and to prevent engine wear, additives are incorporated into the engine oil such as friction modifiers, anti-wear agents, and antioxidants; the latter of which tend to lengthen the effect of the aforementioned additives. Also to reduce the hydrodynamic friction in the piston/cylinder, the viscosity of engine oils has been lowered in recent years, which has increased the dependence on friction modifiers to offset the new boundary layer regime. Organic friction modifiers are generally composed of a polar head group with hydrogen-bonding capability and a non-polar straight hydrocarbon chain for oil solubility. These friction modifiers generally operate at boundary layer conditions by forming thin mono-molecular layers of physically adsorbed polar oil-soluble products or reaction layers which can be readily sheared off and which exhibit a significantly lower friction coefficients compared to typical anti-wear or extreme pressure agents. The most commonly used organic friction modifiers are fatty acid amides, such as oleylamide, fatty amines, such as oleylamine, and fatty acid esters, such as glycerol monooleate.
To improve fuel efficiency, there has been a drive to develop new components which improve the frictional properties of the lubricating oil composition.